3-(3&#39;-lower carboalkoxy-4&#39;-hydroxy-1&#39;-naphthyl)-3-(3&#34;-carboxy-4&#34;-hydroxy-1&#34;-naphthyl)naphthalide

ABSTRACT

THIS INVENTION RELTAES TO THE SYNTHESIS OF NAPHTHOL NAPHTHALIDE INDICATOR DYES AND DYE PRECURSORS BY REACTING A 3-(3&#39;&#39;-LOWER CARBOALKOXY-4&#39;&#39;-OXO-1&#39;&#39;-NAPHTHYLIDENE)NAPHTHALIDE, AN ORGANIC CARBOXYLIC ACID AND A 2-CARBOXYL-1NAPHTHOL IN THE PRESENCE OF BASE TO YIELD THE CORRESPONDING 3=(3&#39;&#39;-LOWER CARBOALKOXY-4&#39;&#39;-HYDROXY-1&#39;&#39;-NAPHTHYL)-3(3&#34;-CARBOXY-4&#34;-HYDROXY-&#34; - NAPHTHYL)NAPHTHALIDE DYE PRECURSOR AND HYDROLYZING THE DYE PRECURSOR TO YIELD THE CORRESPONDING INDICATOR DYE PRODUCT.

3,829,445 Patented Aug. 13, 1974 3,829,445 3-(3'-LOWER CARBOALKOXY 4'HYDROXY-1'- NAPHTHYL)-3-(3"-CARBQXY 4" HYDROXY- 1"-NAPHTHYL)NAPHTHALIDEMichael H. Feingold, Pinehurst, Mass., assignor to PolaroidCorporatiomCambridge, Mass. No Drawing. Filed Dec. 11, 1972, Ser. No.314,094 Int. Cl. C07d 7/06 I 8 Claims US. Cl. 260-343.2 R

ABSTRACT on THE- DISCLOSURE BACKGROUND OF THE INVENTION 1 I (1) Field ofthe-Invention invention relates. to-novel compounds and to .-thesynthesisthereof; Inv particular, it relates to certain derivatives of;,3,'.-(4-, ;hydroXy-.1,'. naphthyl)naphthalides useful, asintermediatesin the synthesis of l-naphthol naphthalide indicator dyes.

(2) Description of the Prior Art Copending U.S. clflatent ApplicationSer. No. 103,865 of Myron S. Simon filed J an. 4, 1971 discloses andclaims certain indicatorldyesderived'from l-naphthols which tfindparticular utilityQas optical filter agents in photographic processesforprotecting an exposed photosensitive material from post-exposurefoggingduring development in the presence of incident Specifically, thel-naphthol indicator dyes disclosed therein comprise 3,3-disubstitutedphthalides and naphthalides wherein the 3,3-substituents are4'-hydroxy-" naphthyl radicals at least one and preferably both of whichpossess a hydrogen-bonding group, such as, a earboxy, hydroxy,sulfonamido or sulfamoyl group substituted on a'carbon atom adjacent tothe 4-hydroxy group. Among such dyes are phthalides and naphthalideswherein one or both of the 4-hydroxy- 1'-naphthyl radicals aresubstituted with a carboxy group in the 3-position and whichadditionally may be substitutedwith an immobilizing group to render thedye substantially non-diffusible in a given photographic processingcomposition. a

One methodfound particularly useful in preparing the.latternaphth'alide-dyes forms thesubject matter of copending U.S.Patent Application Ser. No. 314,097 of -Yunn Chiang etvsal. filedconcurrently herewith. In the method disclosed and claimed therein, amonoester Of a 3-hydroxy-3e(3'--carboalkoxy4'-hydroXy-l'-naphthyDnaphthalide is utilized as the intermediate forreaction with a 2-carboxy-1-naphthol. In a preferred embodiment themethod comprisesreacting a 3-acetoxy-3-(3-carboalkoxy+4'-hydroxy-l'-naphthyl)naphthalide and theselectednaphthol in the presence of a catalytic amount of non-water producingbase to form the corresponding 3-(3-carboalkoxy-4' hydroxy1-naphthyl)-3-(3-carboxy-4"-hydroxy-1"-naphthyl) naphthalide dyeprecursor. The carboalkoxy group of the dye precursor is then convertedto a carboxy group to yield the corresponding indicator dye product. Ina particularly preferred embodiment, the Z-carboxy-l-naphthol reactedwith the monoacetate intermediate contains an aliphatic substituent thatmay be used to adjust the mobility characteristics of the dye product ina particular medium.

The present invention is concerned with another method of preparing suchdyes utilizing a difierent class of intermediates and with a method ofpreparing the intermediates and of preparing monoester derivativesthereof SUMMARY OF THE INVENTION One object of the present invention isto provide a method of synthesizing l-naphthol naphthalide indicatordyes.

Another object of this invention is to provide a method of synthesizingmonoester intermediates useful in the preparation of these indicatordyes.

A further object of this invention is to provide a method ofsynthesizing dehydro intermediates useful in preparing both themonoester intermediates and the indicator dye products.

Other objects of this invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the processes involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others, and the products and compositionspossessing the features, properties and the relation of elements whichare exemplified in the following detailed disclosure, and the scope ofthe application of which will be indicated in the claims.

According to the present invention, methods are provided for thesynthesis of l-naphthol naphthalide indicator dyes and for the synthesisof intermediates useful in the preparation of such dyes.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the presentinvention, it has been found that certain dehydro intermediates, namely,3-(3-lower carboalkoxy-4'-oxo-1'-naphthylidene)naphthalides may besynthesized from the corresponding 3-halo-3-(3'-lower carboalkoxy4'-hydroxy 1'-naphthyl)naphthalides by treating the 3-halo naphthalidewith an acid acceptor. Also, it has been found that the dehydrointermediates obtained may be reacted with an orgainc carboxylic acid toyield the corresponding 3-acyloxy-3-(3'-lowercarboalkoxy-4-hydroxy-1'-naphthy1)naphthalides useful in the method ofaforementioned application Ser. No. 314,097 as the monoesterintermediate-for reaction with a 2-carboxy-l-naphthol to yield thenaphthalide indicator dye precursor. Further, it has been discoveredthat the dehydro intermediates may be employed in a one-pot reactionwith an organic acid and a 2-carboxy-1-naphthol to yield the naphthalidedye precursor directly thereby eliminating the step of synthesizinganother intermediate, such as, the moonester for reaction with theselected naphthol.

3 These three reactions are illustrated in the following schemesdesignated (A), (B) and (C), respectively.

P Ii

000R ooont I II I acid acceptor e.g., pyridine 0 II RCOOH OCR COOR' COOHl Y 1+ ROOOH -i-f base OH. OH

The dehydro intermediates, i.e., the 3-(3-1ower carbo alkoxy-'-oxo-1'-naphthylidene)naphthalides that may be prepared according tothe present invention may be represented by the formula:

wherein R is lower alkyl having 1 to 4 carbon atoms, such as, ethyl,propyl,isopropyl,-'n-butyl,'t-butyl and preferably methyl.

The monoester intermediates, i.e., the 3-acyloxy-3-(3'- lowercarboalkoxy-4'-hydroxy 1'-naphthyl)naphthalides that may be preparedaccording to the present invention may be represented by the formula:

(\Oeoonl wherein -OX is an acyloxy radical derived: fr'ornfan' organicdior monocarboxylic acid, aromatic. or ali-, phatic including branchedor .straight chain saturated or unsaturated aliphatic acids, e.g., asacyloxyradical,

O CR (III) OH wherein Y is hydrogen or an aliphatic group usuallycontaining up to about 20 carbon atoms and Ra' is hydrogen orloweralkyl. V, The aliphatic group, branche d or straight chain, may bealkyl, such as methyl, ethyl, isopropyl, butyl, t -butyl, hexyl,dodecyl, octadecyl or eicosanyl; alkenyl, such as 3-butenyl, 2 methyl1,3 butadienyl, 2-hexenyl and 9" octadecenyl; alkoxy, suchas, ethoxy,butoxy, l-ethoxy-Z- (fl-ethoxyethoxy), hexyloxy, dodecyloxy, andoctadec-v yloxy; and alkoxyalkyl, such as,. methoxyethyl,methoxyethoxyethyl, butoxydodecyl and ,ethoxyethoxyhexadecyl,

Also, the aliphatic group maybe substituted with a solu bilizing group,i.e., the alkyl, alkenyl, alkoxy andalkoxy-v alkyl groups enumeratedabove may be substituted with a solubilizing group, e.g., -OH, -COOH and.SO H.

h v 5 6 Specific exzitnpl I-naphthol 'i'ndic dyes that be prepared 0 tothe method he presen vention are a l 1qws: (9)

In preparing the 3-(3'-COOR'-4'-0xo-1-naphthylidene) naphthalides offormula (I) according to reaction A above, an acid acceptor is added toa solution of a 3-halo- 3-(3'-COOR'-4'-hydroxy-l'-naphthyl)naphthalidein an inert organic solvent. Though the reaction may be conducted atelevated temperature, the removal of the proton from the naphtholic --OHand the removal of the 3-halo group proceeds readily at ambienttemperature, i.e., about 20 to 40 C. to yield the corresponding dehydrocompound. The 3-halo naphthalides employed, as represented in formula IVabove, may be a 3-bromo or preferably a 3-chloro-(3'COOR'-4'-hydroxy-l'-naphthyl)naphthalide wherein R is lower alkyl having1 to 4 carbon atoms, such as, ethyl, propyl, isopropyl, n-butyl, t-butyland preferably methyl. Though the dehydro compound may be similarlyprepared from naphthalides having a different leaving group, forexample, from the sulfonates of a 3- hydroxy-3-(3' COOR-4'-hydroxy-'-naphthyl)naphthalide, such as, a 3-tosyloxy-3-(3'-COO'R-4-hydroxy-1'-naphthyl)naphthalide, the 3-halo naphthalides are particularlyconvenient starting materials. The acid acceptor may be any of thereagents commonly employed for this purpose and preferably is pyridineor triethylamine. To facilitate recovery of the dehydro compoundproduced, the inert organic liquid employed as the solvent for the3-halo naphthalide is preferably one in which the dehydro compound isinsoluble. Particularly useful organic solvents of this type arearomatic hydrocarbons and chlorinated aliphatic and chlorinated aromatichydrocarbons, for example, benzene, toluene, methylene chloride, andchlorobenzene.

T o prepare the monoester intermediates of formula (II) according toreaction B, a 3-(3-COOR-4'-oxo-1'-naphthylidene)naphthalide of formula(I) and an organic carboxylic acid are heated together at elevatedtemperature, usually between about 50 and 150 C. Where the organic acidis a solid, the reaction may be conducted in an inert organic liquidsolvent, for example, an aromatic hydrocarbon, such as, benzene, xyleneor toluene. Otherwise, the reaction is conveniently carried out byheating a slurry of the dehydro intermediate in the liquid organic acid.The organic acid may be a monoor dicarboxylic acid, aromatic oraliphatic including branched or straight chain saturated or unsaturatedacids, for example, benzoic acid, phthalic acid, isophthalic acid,cinnamic acid, a-naphthoic acid, fl-naphthoic acid, acetic acid, butyricacid, caproic acid, capric acid, malonic acid, glutaric acid, sebacicacid, acrylic acid, crotonic acid, vinylacetic aid, methacrylic acid,maleic acid, fumaric acid, muconic acid and so forth. The acid may beunsubstituted or substituted with, for example, amino, hydroxy, halo,mercapto, nitro, cyano, lower alkyl, lower alkoxy, acetyl, phenyl,phenyl substituted with methoxy, nitro, halo or cyano, phenoxy andphenoxy substituted with nitro, halo or cyano. While this method hasbroad application in preparing monoesters derived from a variety ofunsubstituted and substituted organic acids, it is particularly usefulin preparing wherein R is an alkyl group containing 1 to carbon atoms,particularly unsubstituted or monosubstituted alkyl derived from asaturated aliphatic monocarboxylic acid, RCOOH.

In the production of carboxy-substituted l-naphthol naphthalideindicator dye precursors according to reaction C, a3-(3'-COR'-4'-oxo-l'-naphthalidene)naphthalide of formula (I), anorganic carboxylic acid and a Z-carboxyl-naphthol are reacted atelevated temperature in an inert solvent in the presence of base. Toprevent decarboxylation of the carboxynaphthol reactant, the reactiontemperature should not exceed about 85 C., and ordinarily,

8 the reaction is conducted at a. temperature between about 60 and 85 C.The solventemployed' may be any inert organic liquid which is a solventfor-the reactants but preferably, the solvent is an aromatichydrocarbon, such p-Chlorophenylacetic /8-(o-Chlorophenyl) propionic ,3-(m-Chlorophenyl) propionic ,8- (p-Chlorophenyl) propionica-Chloropropionic Crotonic Cyanoacetic 'y-Cyanobutyrico-Cyanophenoxyacetic m-Cyanophenoxyacetic p-CyanophenoxyaceticMethoxyacetic as, benzene, toluene or xylene. The dehydro intermediate,organic carboxylic acid and carboxy-substituted naphthol are generallyreacted in substantially equimolar proportions. The base may be used inamounts ranging between about 0.001 and 2.0 moles and preferably betweenabout 0.05 and 0.15 mole per mole ofnaphthol reactant.

The organic acid reactant may be a monoor dicarboxylic acid, aromatic oraliphatic: including branched or straight chain saturated or unsaturatedacids, such as those mentioned for use in reaction B above. Preferably,it is a saturated aliphatic monocarboxylic acid, RCOOH, wherein R is analkyl group containing 1 to 10 carbon atoms, particularly unsubstitutedand monosubstituted alkyl. Illustrative acids which may be used inpreparing the monoesters of formula (II) and the indicator dyes and dyeprecursors of formula (III) include the following:

Acetic Phenylacetic Acetoacetic Anisic Acrylic o-;3-Anisylpropionicu-Aminoacetic (glycine) m-B-Anisylpropionic Angelic p-fi-AnisylpropionicAdipic n-Butyric p-Aminobenzoic iso-Butyric n-Caproic a-Aminobutyriciso-Caproic Cyanopropionic Chloroacetic Dibromoacetic o-ChlorobenzoicDichloroacetic m-Chlorobenzoic Dihydroxybenzoic(2,2-) p-ChlorobenzoicDihydroxybenzoic(2,5-) a-Chlorobutyric Dihydroxybenzoic(3,4-),B-Chlorobutyric Dihydroxybenzoic(3,5-) Benzoic DimethylglycineBromoacetic Diphenylacetic o-Bromobenzoic Ethylbenzoic m-BromobenzoicEthylphenylacetic a-Bromocaproic Fluoroacetic 'y-ChlorobutyricFluorobenzoic o-Chlorophenoxyacetic Fumaric m-ChlorophenoxyaceticGlutaric p-Chlorophenoxyacetic Heptanoic o-chlorophenylacetic Hexanoicm-Chlorophenylacetic o-Hydroxybenzoic m-Hydroxybenzoic p-Hydroxybenzoic'e-Hydroxybutyric 'y-Hydroxybutyric fi-Hydroxypropionic Iodoacetico-Iodobenzoic m-Iodobenzoic Lactic Lysine MercaptoaceticB-Mercaptopropionic o-Phenylbenzoic 'y-Phenylbutyric ot-PhenylpropionicPimelic Propionic isoPropylbenzoic Sebacic Succinic Toluic (o-, m-, p-)

Trihydroxyb enzoic (2,4,6-)

Trimethylacetic n-Valeric iso-Valeric The Z-carboxy-l-naphthols employedin reaction C may be represented by the formula:

wherein Y has the same meaning given in formula III above. r Among thenaphthols which are particularly useful in the'production of indicatordyes that are relatively or substantially immobile in a given solutionare the alkozysubstituted Z-carboxy-l-naphthols which form the subjectmatter of copending US. Patent Application Ser. No. 174,171 of RichardB. Greenwald filed Aug. 19, 1971. These naphthols may be synthesized bytreating a 1,6- or 1,7-naphthalenediol with an acetylating agent in thepresence of a Lewis acid catalyst to yield the corresponding Z-ace'tylcompound followed by oxidizing the 2-acetyl to a 2-carboxy group andreacting the 2-carboxy compound with an alkyl halide to yield the2-carboxy-6-(or 7-) alkoxy-l-naphthol. These naphthols also may beprepared by treating a 1,6- or 1,7-naphthalenediol in solution in anaprotic solvent with carbon dioxide in the presence of a strong base toform the corresponding 2-carboxy compound which is then reacted with analkyl halide to yield the alkoxy-substituted 2-carboxy-l-naphthol.

Useful as the catalyst are all bases strong enough to form salts withthe naphtholcarboxylic acid (i.e., 2-carboxy-l-naphthol) present in thereaction including weaker bases having a pKa down to but not less thanabout 2, all of which are capable of forming salts with the naphtholcarboxylic acid to some extent. Also, because the intermediates tend tobe sensitive to moisture, the base selected to catalyze the reactionshould not produce or release water during the reaction. Other thaninorganic oxides and hydroxides and other bases that would form "water,any base having a pKa of not less than about 2, including both organicand inorganic materials may be employed. Illustrative bases that may beused as the catalyst include inorganic bases, such as, lithium, sodiumand potassium hydrides or amides, and organic bases, for example,primary, secondary and tertiary aliphatic amines, such as, n-decylamine,di-n-butylamine, triethylamine, n-butylamine, diisopropylamine,piperazines, piperidines, morpholines and aromatic amines, such as,aniline 4- "bromoaniline, N,N-diethylaniline, p-toluidine, N-methyl-'aniline. Particularly useful catalysts are aromatic N- heterocyclicbases, such as, pyridines, picolines, lutidines, pyrimidines,pyridazines, pyrazines, imidazoles and quinolines. Preferred catalystsare the pyridines including pyridine and pyridine substituted with, forexample, hydroxy, amino, halo, lower alkoxy and lower alkyl.

The dye precursor thus obtained may be hydrolyzed, for example, bytreating with an alkaline hydroxide in aqueous or aqueous-organicsolution to convert the 3'-carboalkoxy to a'3'-ca.rboxy group to yieldthe desired indicator dye product. The alkaline hydroxide may be analkaline "earth hydroxide, such as calcium or barium hydroxide, orpreferably, in alkali metal hydroxide, such as, sodium or potassiumhydroxide. Any water-miscible organic liquid may be used to form theaqueous-organic solution, for example, alcohols, such as ethanol,methanol, isopropanol, or water miscible ethers, for example,1,2-dimethoxyethane or tetrahydrofuran.

Though the dye precursor isolated from the reaction solution may behydrolyzed directly to the corresponding indicator dye product, it maybe purified, for example, by crystallization of the crude material in anappropriate solvent prior to the hydrolysis step. Suitable solventsinclude alcohols, such as, isopropanol; combinations of alcohols withchlorinated hydrocarbons, such as, isopropanol and methylene chloridemixture; or with ketones, such as, methanol and actone mixture; andcombinations of nitriles with ethers,'esters, ketones or hydrocarbons,

such, as mixtures of acetonitrile with dimethoxyethane, n-butyl formate,methyl ethyl ketone or benzene.

As noted above, in preparing the indicator dye precursors according toreaction C, the dehyro compound, organic carboxylic acid andcarboxy-substituted naphthol preferably are reacted in substantiallyequimolar proportions. In synthesizing the dehydro compounds accordingPreparation of 3-(3'-carbomethoxy-4'-oxo-1- naphthyl)naphthalide 3chloro 3 (3 carbomethoxy 4-hydroxy-1'- naphthyl) naphthalide (16.7 g.,0.040 mole) was slurried in approximately 100 ml. of benzene at roomtemperature. Pyridine (3.2 g., 0.040 mole) was added to the slurrycausing immediate formation of a red crystalline solid. The red solidwas filtered, washed with benzene and dried. After slurrying in water(in order to remove the pyridine hydrochloride by-product), the productwas again filtered, washed with water and dried, yielding 14.5 g. byweight theory) of red powder.

Analysis.Calculated for C H 'O C, 75.39; H, 3.69; O, 20.92. Found: C,74.96; H, 3.54; O, 20.91.

The material was instantly decolorized on dissolution in methanol,ethanol or acetic acid. The solution in methanol gave on thin layerchromatography, a single spot identical to that obtained with anauthentic sample of the 3-methoxy derivative (as prepared from thechloride and methanol).

Example 1 was repeated using triethylamine instead of pyridine and usingmethylene chloride as the solvent to yield the title compound.

EXAMPLE 2 Preparation of 3-acetoxy-3-(3'-carbomethoxy-4'-hydroxyl'-naphthyl) naphthalide 3 (3carbomethoxy-4'-oxo-1'-naphthylidene) naphthalide (1.0 g.) was slurriedin acetic acid (10.0 ml.) on a steam bath. The red color of thenaphthalide was discharged, and an off-white solid was formed. Theproduct was filtered, washed with benzene and oven dried in vacuo at 60C. The IR spectrum of the product was found to be superimposable withthe IR spectrum of a known sample of 3acetoxy-3-(3-carbomethoxy-4'-hydroxy-1'- naphthyl)naphthalide.

EXAMPLE 3 Preparation of 3 (3-carbomethoxy-4'-hydroxy-1'-napththyl 3(3'T-carboxy-4"-hydroxy-6"-octadecyloxy-l"- naphthyl)naphthalide t 3-(3' carbomethoxy-4'-oxo-1'-naphthylidene) naphthalide (3.82 g.; 0.010mole), 2-carboxy-6-octadecyloxyl-naphthol (4.56 g.; 0.010 mole) andacetic acid (0.60 g.; 0.010 mole) were heated at reflux in 45 ml. ofbenzene for 2.5 hours in the presence of pyridine (approximately 0.0001mole). The reaction solution was then evaporated to dryness in vacuo at40 C. The solid was triturated with 200 ml. of methylene chloride withrapid stirring for 45 minutes and filtered giving 6.5 g. of crudeproduct containing 71% by weight of the title compound, as shown byhydrolysis and measurement of the absorption at 648 nm. in 1:4ethanol:6.4N aqueous sodium hydroxide.

To obtain the indicator dye products, the dye precursor formed above maybe isolated by complete removal of the benzene and hydrolyzed directlywithout purification, for example, by adding aqueous 50% sodiumhydroxide to a solution of dye precursor in isopropanol and refluxingundernitrogenfollowed by cooling and neutralizing with a mixture of icewater, acetic acid and hydrochloric acid. To facilitate finalpurification of the dye product, however, the dye precursor usually ispurified prior to the hydrolysis step by crystallization from anappropriate solvent, for example, methyl ethyl ketone or dimethoxyethanecombined with acetonitrile. Alcohols such as isopropanol or Z-butanolmay also be used. Particularly preferred as the crystallization solventis 60:40 butyl formatezacetonitrile, since this system gives highrecovery (80-82%) of highly pure precursor (96+%) in a singlecrystalliaztion. Final purification of the dye product may be carriedout by heating the crude dye in methanol at reflux, cooling, addingadditional methanol and filtering the final dye from the methanolslurry.

The 3-halo naphthalides used in reaction A may be synthesized accordingto the method disclosed in copending US. Patent Application Ser. No.192,638 of Richard B. Greenwald filed Oct. 26, 1971, by halogenation ofa 3 hydroxy-3-(3-lower carboalkoxy-4'hydroxy-l'-naph thyl)naphthalide tothe corresponding 3-halo naphthalide, preferably, 3-chloro or 3-bromo.This may be accomplished by treating the 3-hydroxy naphthalide withphosphorus pentachloride, thionyl chloride, phosphorus pentacloride,N-chlorosuccinimide, phosphorus oxychloride, sulfuryl chloride,phosphorus tribromide, N-bromosuccinimide, aluminum bromide, aluminumchloride, boro tribromide, N-bromocaprolactam, cupric bromide or otherconventional chlorination or bromination reagent.

The 3-hydroxy-3-(3'-lower carboalkoxy-4'-hydroxy-l'-naphthyl)naphthalides may be synthesized by forming a complex of al-hydroxy-Z-alkyl naphthoate (Z-carboalkoxy-l-naphthol) by reacting thenaphthoate with anhydrous aluminum chloride followed by the addition ofsolvent, such as, nitrobenzene. Naphthalyl dichloride (3,3-dichloronaphthalide) is then added to the solution containing thenaphthoate as an activated complex to form the 3-hydroxy-(3-lowercarboalkoxy 4' hydroxy-1'- naphthyl)naphthalide.

The 3 chloro-3-(3'-carbomethoxy-4'-hydroxy-1-naphthyl)naphthalide usedin Example 1 was prepared as follows:

A suspension of 16.0 g. of3-hydroxy-3-(3'-carbomethoxy-4'-hydroxy-1'-naphthyl)naphthalide-1,8 Washeated under reflux with stirring with a solution of 9.5 g. of thionylchloride in 100 ml. of methylene chloride, containing three drops ofN,N-dimethylformamide, for 30 minutes, when a solution occurred. Oncooling a solid crystallized from the purple solution. Hexane was addeduntil no more solid precipitated. The solid was filtered and washedfirst with a small amount of methylene chloride and then with hexane,yielding 16.7 g. of the gray crystalline chloride. The conversion wasquantitative as shown by thin layer chromatography.

The 1 hydroxy-6-octadecyloxy-2-naphthoic acid employed in Example 3 wasprepared by adding sodium methoxide (67.4 grams, 1.35 mole) to asolution of 1,6- dihydroxynaphthalene (100 gms., 0.625 mole) in 900 ml.of dry carbon dioxide gas. A steady flow of carbon dioxide wasmaintained throughout the reaction. Approximately 125 ml. ofdimethylformamide was distilled and the mixture was then refluxed for 15minutes and an additional 125 m1. of solvent removed. The solution wascooled and the flow of carbon-dioxide stopped. The reaction mixture wasacidified with concentrated hydrochloric acid and then poured onto about2000 gms. of ice. The precipitated dark solid was filtered and dried andthen triturated with 1 liter ofboiling benzene and filtered free of darkimpurities. Recrystallization from water gave 1,6-;'

dihydroxy-Z-naphthoic acid as a white solid (melting range 220-221 C.).

To a well-stirred slurry of 1,6-dihydroxy-2-naphthoic acid (5.1 gms.,0.025 mole) in 50 ml. of dry isopropyl alcohol under nitrogen was addedpotassium t-butoxide (5.65 gms., 0.050 mole) The mixture was heated toreflux and stirred 10-15 minutes and then octadecyl bro; mide (8.35gms., 0.025 mole) was added. The reaction was refluxed for 5 hours,cooled and acidified wi t hf20%' hydrochloric acid. The solid whichprecipitated was"fil,-, tered and dried and recrystallized from absoluteethanol to give 38 gms. of grey solid Further' recrystallization fromchloroform gave 2.3 gms. of l-hydroxy-6-oc'tadecyloxy-2-naphthoic acidas a white solid (melting range 164- 165C.).

As noted above, the indicator dyes produced in accordance with thepresent invention are useful as optical filter agents in photographicprocesses, and because of their relatively high pKa, are particularlyuseful in diffusion transfer processes employing highly alkalineprocessing solutions. Their use as optical filter agents in photographicprocesses is disclosed and claimed in copending US. Patent ApplicationSer. No. 103,392 of Myron S. Simon and David P. Waller, filed Jan. 4,1971, now US. Pat. No. 3,702,245. Certain l-naphthol naphthalidesincluding carboxy-substituted l-naphthol naphthalides form the subjectmatter of copending US. Patent Application Ser. No. 103,865 of Myron S.Simon also filed Jan. 4, 1971,

The method comprising reaction A for preparing dehydro naphthalides andthe method comprising reactiorrB for preparing 3-acyloxy naphthalidesare claimedin my copending US Patent Applications Ser. Nos. 313,963 and314,095 respectively, both filed concurrently herewith.

Since certain changes may be made in the above procses without departingfrom the scope of the invention herein involved, it is intended that allmatter contained in the above description shall be interpreted asillustrative and not in a limiting sense. i

What is claimed is:

1. A process which comprises reacting (a) a 3-(3'- lowercarboalkoxy-4'-oxo- 1 '-naphthylidene) naphthalide; (b) an organicmonocarboxylic acid, and (c) a 2-carboxyl-l-naphthol, in substantiallyequimolar proportions in an inert organic solvent at a temperature not"exceeding C. in the presence of about 0.0001 to 2.0 moles of non-waterproducing base having a pKa of not less than about 2 to form thecorresponding 3-(3-lower carboalkoxy-4-hydroxy-1-naphthyl) -3-(3 -lowercarboxy-4"-hy-. droxy-1-naphthyl)naphthalide dye precursor. I.

2. A process as defined in claim 1 wherein saidacid (b) is RCOOH whereinsaid R is an alkyl group containing 1 to 10 carbon atoms.

3. A process as defined in claim 2 wherein said 3- lower carboalkoxy ofsaid naphthalide (a) is '3'-carbomethoxy.

4. A process as defined in claim 3 wherein said l-naphthol (c) is6-octadecyloxy-2-carboxy-1-naphthol,

5. A process as defined in claim 4 wherein said R of said acid, RCOOH,is methyl.

6. A process as defined in claim 1 wherein said base is pyridine. v

7. A process as defined in claiml wherein said inert organic solvent isan aromatic hydrocarbon.

8. A process as defined in claim 1 wherein said tem-- perature isbetween about 60 and 85 C.

No references cited.

HENRY R. JILES, Primary Examiner M. A. M. CR-OWDER, Assistant Examiner

